APPLICANT'S ABSTRACT: Tobacco smoking represents a major health problem in view of its long term harmful effects. Most tobacco users are well aware of the hazards of smoking yet they continue this life threatening habit, presumably because of their dependence upon nicotine. The specific aim of this proposed research is to determine the effects of tobacco smoking and withdrawal on the topographic electroencephalogram (EEG) and its relationship to behavioral alertness. The former is a microcomputer generated map of the electrical activity at specific regions of the brain as measured by scalp disc electrodes. Normal adult tobacco smokers of mixed sex will be recruited in groups of eight. Minority representation will be included as part of the experimental design. A controlled study will be performed in which an initial recording will be taken after zero, 1/2, 12, 24, 72 and 168 hours of abstinence from smoking. Another recording will be taken after the volunteer smokes either a zero, low or high nicotine containing research cigarette. The topographic mapping will be analyzed to determine the degree and location of specific effects of nicotine in tobacco smoking on brain activity. These EEG changes will be obtained with the eyes closed so as to be able to determine spontaneous alterations in the frequencies of alpha as well as other EEG rhythms. Behavioral alertness with the eyes closed will be measured using the subject's estimate of the number of correct unusual presentations for the oddball tones as a continuous performance task. Both the auditory evoked potential (P300) and the contingent negative variation potential in response to pressing a lever to an oddball tone will be measured and correlated with the subject's actual performance. The hypothesis of this research is that tobacco smoking will cause an increase in the frequency of brain alpha electroencephalographic activity consistent with an awake relaxed state.The cortical areas most affected will be the occipital, parietal, and central regions. Central midline alpha due to tobacco smoking is a new phenomenon which preliminary research in preparation for this grant application has already obtained, but needs more effort to document and expand to different periods of tobacco abstinence.